PC Musician
Technique : PC Musician
If you're after bigger-sounding tracks,
read on, as we discover plug-ins that manipulate stereo information to play tricks with your mix...
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There's never been a bigger choice of PC software
that can enhance the spatial characteristics of your mixes than there is
now. The options range from simple stereo-widening plug-ins to make
your mixes seem 'bigger' and pseudo-stereo tools to turn mono sources
into stereo destinations, through to sophisticated 3D tools that can
shift sounds beyond your stereo speakers and move them around you in
real time.
Let's start with the easiest imaging effect of all:
stereo narrowing. While classical recordings get a natural stereo image
direct from the microphones and many electric and acoustic instruments
are recorded in mono and placed in the mix using a pan control, many
keyboards and synths already have stereo effects that spread them across
the entire stereo image and swamp the mix. Some musicians convert these
sounds to mono to prevent this, but a more sophisticated approach is to
pan the left and right channels away from the channel extremes and more
towards the central mono position. This will narrow the image and make
such instruments easier to fit into a mix, while leaving them in stereo.
The same technique is often helpful if you use several reverb or
early-reflection effects in a song, to give each one its own space
without allowing it to dominate.
Some applications, such as Gigastudio
already provide a dedicated Width control (in addition to a normal Pan
control) for each mixer channel, that simultaneously moves both left and
right signals inwards to narrow the stereo image. However, if your
application of choice doesn't have these controls, there are several
simple freeware plug-ins that do the job nicely without altering the
audio in any other way.
Narrowing the stereo image of sounds like keyboard pads, using plug-ins such as GPan, can significantly reduce clutter in your mixes.
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One of the simplest is GSonic's GPan (www.gsonic.com/gse/gse.html),
a Direct X plug-in that provides separate gain and pan controls for
each stereo channel (see screen, bottom left). Destroy FX's Monomaker (www.smartelectronix.com/~destroyfx)
has more graphic finesse, with its two stretchy globules indicating the
mono merge effect (see main header pic, left), plus a separate pan
control It's in VST format, so you just drop it into your VST plug-ins
folder rather than installing it.
More sophisticated still is Stereo Tools (www.kellyindustries.com),
a tiny VST plug-in from Kelly Industries, with separate volume, pan,
phase invert and mute controls for each channel, plus buttons for mono,
channel swap, gang pan, gang volume, and Mid & Side. The latter is
useful if you have M&S recordings that need converting to stereo, or
to use before or after another plug-in effect. You can automate GPan inside applications like Sonar
that support Direct X v8, for silent real-time adjustments, but the two
VST plug-ins don't have ramp or zero-detection functions and therefore
may generate a little noise when their controls are moved in real time
inside VST-compatible hosts.
Another more specific tool for stereo narrowing is the freeware Otium FX Basslane (www.otiumfx.com)
that I mentioned in PC Notes October 2006, which collapses the stereo
width below a user-defined frequency, to keep bass in mono for vinyl
pressing, and to retain low-end punch.
Of course, you may not need a separate narrowing
plug-in at all, since many stereo widening plug-ins also let you reduce
width below 100 percent, as well as expanding it. Examples include
Steinberg's Stereo Expander, PSP's Stereo Controller, and Waves' S1 Stereo Imager, all of which bring us neatly to...
Plug-ins designed for widening the stereo image
generally fall into two camps. Some are intended more as effects to be
used on individual tracks during the mixing process, that push sounds
'beyond the speakers'. I'll cover these in the next section. The
remainder are intended for correcting more subtle errors made at the
recording stage, such as an artificially narrow image of a live ensemble
performance captured by mics, or to simply add more 'space' to a mix.
The latter type generally take great pains to avoid any changes to the
overall tonality of your recordings, as well as 'phasey' effects, so
they can (with care) be used during mastering on final stereo mixes.
From ultra-simple to highly sophisticated, stereo widening plug-ins like PSP's Stereo Controller can be used both to enhance 'space', for special effects, and during mastering, to correct recording errors.
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Widening is mostly achieved by manipulating the Mid
and Side signals. The Mid signal is common to both stereo channels and
therefore appears in the centre of the stereo image, while the Side
signal is the difference between the two stereo channels. By inverting
the phase of each channel and adding a small amount of this
phase-inverted signal to the opposite channel, you can add spaciousness
to a mix.
Mid/Side widening plug-ins generally retain a high
level of mono compatibility, which is important, because you don't want
your latest hit to sound odd when broadcast to the huge number of mono
radios still out there. One simple example is Steinberg's Stereo Expander, bundled with both Cubase and Wavelab,
which has a single horizontal Width slider. At the central position,
your stereo image is unaltered; moving it to the left narrows the stereo
width right down to mono if required, while moving it to the right
increases the Side (difference) signal, making the image sound a lot
more spacious. Another example is PSP's Stereo Controller plug-in (above), part of the PSP Stereo Pack (www.pspaudioware.com/ plugins/stereopack.html) along with the Pseudo Stereo and Stereo Enhancer plug-ins mentioned later, plus the handy Stereo Analyser goniometer display of level, phase, and mid/side components.
Stereo Controller fulfils all the
conditions mentioned earlier for correcting subtle errors, offering
width adjustment from zero percent (mono) through to 400 percent (the
difference signal is amplified by 12dB), channel balance control, and
pan controls for both side and mid signals, so you can alter the two
sides of the stereo image without altering the central image, or
centralise a stereo image without altering the mix level balance.
Although initially confusing (especially since the side and mid pan
controls are labelled 'Stabil' and 'Center' respectively), I've found
the Stereo Controller very useful over the years for tweaks during mastering.
Waves' S1 Stereo Imager (www.waves.com)
provides a similar set of controls with less confusing labels, such as
Asymmetry and Rotation, along with an associated display that provides
visual feedback as controls vary the stereo image, showing the output
positions of central, left and right sounds and their new levels.
S1 also has a very useful Shuffle control
that lets you further increase stereo width at lower frequencies
(typically below 600Hz, as set by the associated Frequency control).
This compensates for the fact that the ear is less sensitive to stereo
bass effects, so you can either use Shuffle to sharpen stereo imaging in
an existing mix, while leaving its width unaltered, or further widen
the bass end, for a feeling of increased spaciousness at the expense of
less precise imaging. Shuffling only affects non-central sounds, so you
can use it to widen the bass end of other instruments in the mix without
disturbing the level or imaging of centrally panned kick drum and bass
guitars (this should keep the 'mono bass is tighter' camp happy).
S1, which is my favourite stereo imaging
tool for mastering purposes, can also be switched to M& S (Mid &
Side) mode and used in a plug-in chain with other treatments such as
EQ, to provide frequency-dependent control over stereo width, or to
equalise central or side sounds independently..
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Pseudo-stereo: Turning Mono Into Stereo?
'Pseudo-stereo' is a completely different treatment
from the others discussed here, designed to turn mono signals into
stereo ones, to make them sound 'bigger'. Various techniques can be
used. One of the simplest is to make a couple of copies of a mono audio
track, delay them both slightly, pan them left and right, and possibly
phase-invert one of them as well. You can do this manually or with a
plug-in such as Storm's freeware STThick (www.stormrecordingstudio.co.uk), which provides control over the delay time and mix level of the original versus the new, cloned versions. Voxengo's freeware Stereo Touch (www.voxengo.com)
is similar in offering two delays, but with the added sophistication of
variable low-pass filtering, to help you make the direct signal stand
out, variable gain on the second delay, and variable pan and width
controls (see screenshot, right).
Another common technique is to use comb filtering, splitting the
original signal into a set of frequency bands, some of which are then
panned left and some panned right. A classic example is PSP's Pseudo Stereo,
which offers a continuously variable frequency of 20Hz to 1kHz for the
lowest comb (lower values further widen the stereo image, until you hear
the effect as two distinctly separate sounds), plus a Treble Emphasis
control to compensate for low-end anomalies, at the expense of mono
compatibility. Their Stereo Enhancer uses similar comb-filtering techniques, but optimised for stereo signals, and I find both extremely effective.
Izotope's Ozone mastering suite (www.izotope.com)
has a section devoted to multi-band stereo Imaging, complete with a
Vectorscope (goniometer) display and phase meter. You can enable between
one and four frequency bands, each with its own controls, to alter
apparent stereo width. With a single band, you achieve standard
narrowing and widening effects, but with more than one band you can
create pleasing frequency-dependent width effects. For instance, you
could specifically widen frequencies above a few kilohertz to add some
mix 'space' without muddying the mid-range and bottom end, or make the
low-end narrower. Such multi-band imaging can also be very useful in
restoration work, when you want to give some separation to different
instruments from an old mono recording. (See screenshot, bottom.)
QSound's Q123 is part of the QTools/AX
suite mentioned in the main body of this article, and is a
mono-to-stereo plug-in that takes a mono signal and uses the famous
QSound algorithms to convert it to a wide pseudo-stereo version, with a
Center control that pans the central part.
If you're looking for more extreme imaging effects, consider the freeware Klanglabs Multiband Stereo Faker
(http://klanglabs.siliconemusic.com), which provides six filters
running in parallel, with resonance and high-pass, band-pass,
band-reject, and low-pass options. The output of each of these can be
manually panned, or autopanned using individual LFOs with frequency and
depth controls. Each band can also be delayed with feedback. You can use
these features to separate instruments in a combined mix, to create
slowly meandering sound masses or shimmering movement, or for drum-loop
mangling.
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Beyond The Speakers
To move sounds such that they appear to originate
from positions beyond the two stereo speakers, above or below them, or
even behind the listener, you need rather more sophisticated techniques
that analyse the way the human head and ears react to incoming sound
from different points in space. These take account of timing differences
between the left and right ears, the 'shadowing' effect of the head,
and in particular the role of the external parts of the ears, which act
like complex, direction-dependent tone controls. Such phenomena are
generally measured using a 'dummy head' with microphones fitted in its
'ears', while a mono sound source is moved around it, and are stored as
HRTFs (Head Related Transfer Functions).
  
QSound's plug-ins and utilities are extremely
effective if you want sounds placed 'beyond the speakers' for spot
effects or ultra-wide sound beds.
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The two most prominent hardware systems that offer
'beyond the speakers' effects are Roland's RSS (Roland Sound Space) and
QSound from Canadian company QSound Labs. The latter is perfect for our
purposes, since it's also available in plug-in form. QSound 3D audio has
featured to great effect on various albums, including Madonna's Immaculate Collection and Sting's Soul Cages,
and the company's algorithms have also been licensed to manufacturers
including Creative labs, for use in Soundblaster products, and Sega, for
their games.
I originally reviewed the QSound plug-ins way back in SOS
March 1997 and they are still going strong today, although early
adopters will no doubt be pleased to hear that both the floppy install
disk and the insistence that you insert the original CD-ROM each and
every time you used one of the plug-ins have long since been abandoned. QTools/AX (www.qsound.com) now retails at the very reasonable price of $79.95 and is a suite of three PC Direct X plug-ins: one (QXPander) is for widening existing stereo signals beyond the speakers, the second (QSys)
is a 'super-pan' control for mono signals, and the third (Q123) is for
creating a stereo signal from a mono one (see the 'Pseudo-Stereo' box
for more details on this plug-in). They are designed for loudspeaker
playback (not headphones: a newer technology does do this, but isn't
available in plug-in form) and work with sample rates from 6kHz to
48kHz.
QXPander is the one to use for stereo
submixes, instruments or final mixes, as it can push the extremes of the
mix way beyond the speakers. There's no width control as such (although
the more stereo width on your original stereo input, the more extreme
the effect), but the Center control provides wet/dry balance for the
central image. When fully 'wet', the 3D effects are more extreme, but
for full mixes a dryer setting will provide better mono compatibility.
Meanwhile, the variable-frequency Crossover control lets lower
frequencies bypass the effect, for more natural results on full mixes.
QSys takes a mono signal and lets you pan
it using a 'super' Pan control that displays the normal speaker
positions but allows you to move your sounds beyond them to either side.
Like QXPander, it also has a Crossover slider that bypasses
the effect on lower frequencies, for greater mono compatibility. Sadly,
you can't automate these Direct X plug-ins, although QSound do sell QCreator, a bargain $19.95 stand-alone version of QSys
that will load a mono WAV or AIFF file and convert it to a QSound
stereo version, after you draw in your automated moves using its
click-and-drag Pan Line.
Like all trickery of this type, the positioning of
sounds beyond the speakers will be vague or even lost if you rotate your
head, or if your room has lots of unwanted early reflections, or you're
not sitting in the mixing sweet spot. However, the effect is always
super-wide, and when you do sit in the right spot the results are
uncannily good, producing sounds that appear to come as far beyond the
speakers as they are far apart from each other. These plug-ins are
highly recommended for spot effects, percussion and all-enveloping sound
washes.
3D Positioning
Like QSound's 'beyond the speaker' technology, 3D
positioning plug-ins that not only offer pan adjustments from side to
side, but also forward into the distance, behind you, and even above and
below, generally start life based on Head Related Transfer Functions.
Several Universities offer free HRTF data sets based on their own
research, and some plug-in developers use these as a basis for their own
3D products.
Spin Audio's 3D Panner Studio (www.spinaudio.com)
provides an easy-to-use display that lets you drag and drop objects
anywhere in the horizontal (front to back and left to right) plane, as
well as the vertical plane (up and down), for the complete 3D headphone
experience. It also features Far and Near field modes, Distance
simulation and Interaural Time Difference correction for positioning
sounds 'inside the head', and supports switchable HRTF (Head-Related
Transfer Function) data sets from different researchers. It has a
special Pad display that lets you choose different instrument icons for
each audio track and view up to 32 of them simultaneously, to see your
complete 3D mix in a single window.
For sophisticated 3D positioning of sounds, plug-ins such as Spin Audio's 3D Panner Motion Effects should be considered.
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Spin Audio's £53 3D Plug-ins bundle takes
motion effects even further, offering 3D delays, whose six taps can be
separately positioned in the 3D field, a 3D chorus with six
independently modulated stereo delay lines offering similar
capabilities, and 3D panner motion effects, which, as the name suggests,
lets you automate your movements, either using the facilities of your
sequencer or via the plug-in's built-in oscillators.
All of the plug-ins include lots of intriguing
presets, and there's no denying that the motion controls add some very
pleasing spatial enhancement, while the 3D delays and chorus offer
plenty of unusual scattering effects. However, the effectiveness of the
3D experience varies from person to person (the ideal would be for each
person to have their own HRTF data set created using tiny mics mounted
in their own ears, and only listen using that, but of course this is
wildly impractical). Despite hours of experimentation and listening
through several different sets of headphones, I've yet to hear any sound
travel behind me, or above and below me (perhaps due to an
untypically-shaped head and ears!), so, as they say, your mileage may
vary.
Wave Arts' Panorama (www.wavearts.com)
takes the 3D experience even further, by providing optional crosstalk
cancellation so that loudspeaker listeners can enter the experience
(normally the effect is lost on stereo loudspeakers, because you can
hear both through each ear), as well as adding a selection of
early-reflection and reverberation options, so you can place your sounds
in a selection of virtual 3D spaces. Just as important for simulating
moving objects is the Doppler shift facility, which recreates the
increase in pitch as something comes closer at speed, and the drop in
pitch once it passes you and moves away.
Panorama's interface is clear and
informative (see screen on first page of this article), and there's a
lot on offer here for $199. However, while the Doppler shifts are
realistic enough to induce motion sickness within a few seconds at more
extreme settings, I still can't hear the 'behind' or up/down cues. You
may be luckier.
Ideal for film, TV and games design, plug-ins that
feature Doppler pitch-shift offer exaggerated and obvious movement
effects that everyone will find effective.
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If you need to create specific moving sounds for
film, TV, or game effects, such as vehicles passing, or aircraft and
spaceship flybys, you may prefer to concentrate on the more obvious
Doppler pitch-shift effects, and there are several plug-ins that can
oblige.
Waves' Doppler (www.waves.com)
is an extremely effective plug-in with a set of 'Reality' controls
based on the laws of physics, such as distance attenuation, amount of
pitch shift, air damping for the high-frequency loss of distant objects,
and reverb. It provides a main graphic display similar to that of the S1 Stereo Imager,
but features a superimposed line with draggable start, centre, and end
points for programming in your movements. The effect can either be
looped, or triggered as a one-shot event, manually or automatically.
For more extreme motion effects, take a look at the Doppler plug-in from the GRM Tools Classic VST Bundle (www.grmtools.org),
whose effects have been used in several major films (see screen above).
It incorporates a bank of 16 presets, between which you can morph
according to a user-defined speed. The Doppler graphic display
shows what looks like a planet and two orbiting moons (the latter
indicating the position of the left and right audio channels), with
adjustable separation (width). You can either grab the planet and move
it around manually while its moons follow at a user-defined speed, or
use the Circle Frequency/Amplitude controls to generate automatic
orbits, both with adjustable Amplitude and Doppler variation.
I have to say that GRM's Doppler plug-in is my favourite for motion extravaganzas, either with some automated dragging or using the circle controls to create continuous whirling effects, especially with QSound's QXPander patched in afterwards to whizz objects around way beyond the speakers. Don't try this after a heavy meal, though!
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